Fait mathématique: 1663 is the number of partitions of 41 in which no part occurs only once.
Culture générale: 1663 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: July 20th is the day in 1969 that a cease fire is announced between Honduras and El Salvador, 6 days after the beginning of the "Football War".